MRI compatible guide wire

ABSTRACT

An improved intracorporeal device such as a guide wire or other guiding member for use within a patient&#39;s body that is at least in part visible under magnetic resonance imaging (MRI) but is not detrimentally affected by the imaging is disclosed. The intracorporeal device has a non-conductive proximal core section, an essentially non-magnetic metallic distal core section that is preferably more flexible than the proximal core section, and that has an MRI visible member or coil in the distal section.

CROSS-REFERENCES TO RELATED APPLICATIONS

This is a continuation of co-pending application Ser. No. 10/335,783,filed Jan. 2, 2003, which is a continuation of application Ser. No.10/034,715, filed Dec. 26, 2001, now U.S. Pat. No. 6,799,067, all ofwhose contents are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates generally to the field of medical devices, andmore particularly to a guide wire for advancing a catheter or otherintraluminal device within a body lumen in a procedure such aspercutaneous transluminal coronary angioplasty (PTCA) or stent deliverywhich is observed by Magnetic Resonance Imaging (MRI).

BACKGROUND OF THE INVENTION

Conventional guide wires for angioplasty and other vascular proceduresusually comprise an elongated core member with one or more taperedsections near the distal end thereof and a flexible body such as ahelical coil disposed about the distal portion of the core member. Ashapeable member, which may be the distal extremity of the core memberor a separate shaping ribbon which is secured to the distal extremity ofthe core member, extends through the flexible body and is secured to arounded plug at the distal end of the flexible body. Torquing means areprovided on the proximal end of the core member to rotate, and therebysteer, the guide wire while it is being advanced through a patient'svascular system.

In a typical PTCA procedure, a guiding catheter having a preformeddistal tip is percutaneously introduced into the cardiovascular systemof a patient in a conventional Seldinger technique and advanced thereinuntil the distal tip of the guiding catheter is seated in the ostium ofa desired coronary artery. A guide wire is positioned within an innerlumen of a dilatation catheter and then both are advanced through theguiding catheter to the distal end thereof. The guide wire is firstadvanced out of the distal end of the guiding catheter into thepatient's coronary vasculature until the distal end of the guide wirecrosses a lesion to be dilated, then the dilatation catheter having aninflatable balloon on the distal portion thereof is advanced into thepatient's coronary anatomy over the previously introduced guide wireuntil the balloon of the dilatation catheter is properly positionedacross the lesion. Once in position across the lesion, the balloon isinflated to a predetermined size with radiopaque liquid at relativelyhigh pressures (e.g., greater than 4 atmospheres) to press thearteriosclerotic plaque of the lesion against the inside of the arterywall and to otherwise expand the inner lumen of the artery. The balloonis then deflated so that blood flow is resumed through the dilatedartery and the dilatation catheter can be removed therefrom.

A major requirement for guide wires is that they have sufficient columnstrength to be pushed through a patient's vascular system or other bodylumen without kinking. However, they must also be flexible enough toavoid damaging the blood vessel or other body lumen through which theyare advanced. Efforts have been made to improve both the strength andflexibility of guide wires to make them more suitable for their intendeduses, but these two properties are for the most part diametricallyopposed to one another in that an increase in one usually involves adecrease in the other.

Currently, x-ray fluoroscopy is the preferred imaging modality forcardiovascular interventional procedures because no other imaging methodhas the temporal or spatial resolution provided by fluoroscopy. However,x-ray imaging has many drawbacks for both the patient and the clinician.The iodinated contrast agents employed in x-ray fluoroscopy arenephrotoxic with a low but measurable incidence of short-term renalfailure and allergic reactivity. The ionizing radiation from the x-rayfluoroscopy can be an issue for the patient during protracted orrepeated interventions and is a daily issue for the interventionalistand staff who must cope with the burden of personal dose monitoring andwearing lead shielding.

The use of MRI for observing interventional procedures has beenperformed for balloon angioplasty and stent placement. The use of thisimaging modality is quite attractive because it eliminates some of theproblems inherent with x-ray imaging. On the other hand, conventionalguide wires which are suitable for x-ray fluoroscopy are not suitablefor use in MRI observed interventional procedures due to their magneticattraction, large magnetic susceptibility artifact, and potentialheating when exposed to RF energy.

What has been needed and heretofore unavailable is a guide wire which issafe and compatible for use in conjunction with MRI. The presentinvention satisfies these and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to an intracorporeal device such as aguide wire which is safe, compatible and readily visible with MRI. Anintracorporeal device embodying features of the invention preferably hasan elongated member with an electrically non-conductive proximalsection, an essentially non-magnetic distal core section, and a metalliccoil disposed about and secured to the distal core section with a smallmagnetic susceptibility to act as an MRI visible marker. That is, thecoil or a marker thereon has a magnetic susceptibility that facilitatesthe observation thereof within the patient under MRI.

The distal end of the proximal non-conductive core section and theproximal end of the non-magnetic but conductive distal core section canbe secured together by any non-conductive means including polymeric ormetallic sleeves so long as the joint between these members results in atorque transmitting relationship therebetween.

The selection of materials for component parts of the intracorporealdevice, such as a guide wire, including the proximal section, the distalsection and the MRI visible member secured to the distal section arebased upon the mechanical and physical properties needed for theintended use. The materials from which the MRI compatible device is madeneed to overcome three basic factors: magnetic attraction of magneticmembers, RF heating effects of conductive members, and visualizationunder MRI.

Forming the proximal section from non-conductive, non-metallic materialand the distal section and MRI visible member from non-magneticmaterials resolves the magnetic attraction of these members during MRI.The non-conductive, non-metallic nature of the proximal core section andthe length of the distal core section alone or in conjunction with theMRI visible member resolve the RF heating of these members. Controllingthe level of magnetic susceptibility of the material from which the MRIvisible member is formed resolves the visualization issue.

Suitable materials for the non-conductive proximal section of theintracorporeal device include optical fibers (single or a bundle offibers), fiberglass, carbon fiber-epoxy composites, composites oforiented polyethylene fiber (e.g., Spectra®), composites of polyaramidefiber (e.g., Kelvar®) and composites of these materials with engineeringresins such as polysulfone, polyethersulfone, polyetherimide,vinylester, cyanate ester, phenolic, polyurethane, polyimide andpolyetheretherketone. The MRI visible member or marker and preferablyalso the distal section are formed of suitable non-magnetic materialsthat may be electrically conductive. Suitable materials include one ormore metallic materials selected from the group consisting of platinum,nitinol, niobium, titanium, tantalum, zirconium, iridium, aluminum,silver, gold, indium, and alloys thereof.

The distal core section and the tip coil are formed of suitablenon-magnetic conductive materials having the correct amount of magneticsusceptibility artifact for accurate imaging. The volumetric magneticsusceptibility suitable for visualization under MRI for these structuresis less than or equal to about 280×10⁻⁶ (SI), and preferably less thanabout 245×10⁻⁶ (SI).

The intracorporeal devices embodying features of the present inventionare in part readily visible under MRI and they have desirablecharacteristics for performing intracorporeal procedures. These andother advantages of the invention will become more apparent from thefollowing detailed description thereof when taken in conjunction withthe following exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, partially in section, of a guide wirethat embodies features of the present invention.

FIG. 2 is an enlarged, side elevational view, partially in section, ofthe junction between the proximal and distal core sections of the guidewire shown in FIG. 1 taken within line 2-2.

FIG. 3 is a cross-sectional view of the guide wire shown in FIG. 1 takenalong the line 3-3.

FIG. 4 is a cross-sectional view of the guide wire shown in FIG. 1 takenalong line 4-4.

FIG. 5 is a cross-sectional view of the guide wire connection shown inFIG. 2 taken along the line 5-5.

FIG. 6 is a cross-sectional view of the guide wire shown in FIG. 1 takenalong line 6-6.

FIG. 7 is a side elevational view, partially in section, of analternative distal core section having non-conductive junctions betweenconductive core segments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-6 illustrate an embodiment of an MRI compatible guide wire 10embodying features of the present invention that is used in a patient'sbody lumen, such as an artery or vein. The guide wire 10 generallycomprises an elongated, relatively non-conductive proximal core section11, a relatively short, non-magnetic, metallic distal core section 12, apolymeric connecting element 13 securing together the distal end 14 ofthe proximal core section 11 and the proximal end 15 of the distal coresection 12. A helically shaped metallic coil 16, formed at least in partof non-magnetic material, is disposed about and secured to the distalcore section 12. The coil 16 is secured at its distal end by a roundedbody 17 of solder, weldment, or adhesive, at an intermediate location bya mass 24 of solder or adhesive, and at its proximal end by a mass 19 ofsolder, adhesive or other suitable material that joins the coil 16 tothe distal core section 12.

The guide wire 10 shown in FIG. 1 generally has conventionalintravascular guide wire features and the particular embodiment shown iscommonly called a “floppy” guide wire due to the shaping ribbon 23 whichextends from the distal core section 12 to the rounded mass 17. Thedistal end of the shaping ribbon 23 is secured to the end of the coil 16by the mass 17 and the proximal end thereof is secured by intermediatemass 24 of connecting material which also secures an intermediateportion of the coil 16 to the distal core section 12. The distal coresection 12 optionally has at least one tapered section 25 with smallertransverse dimensions in the distal direction. The rounded distal tip 26of the distal core section 12 is so configured to prevent the end of thedistal core section from extending through the spacing between the turnsof the coil 16 when the guide wire 10 passes through tortuous anatomy.

The polymeric connecting element 13, which is shown in detail in FIG. 2,is a polymeric member that is disposed about and secured to theundulated distal end 20 of the proximal core section 11 and theundulated proximal end 21 of the distal core section 12. This embodimentof the connector element 13 generally has a cylindrical exterior 22 thathas an outer diameter about the same as the outer diameter of the coil16 and the outer diameter of the proximal core section 11. The ends 20and 21 of the proximal core section 11 and the distal core section 12may be given an undulated shape as shown in FIG. 2 to provide amechanical interlock or friction fit with the polymeric material of theconnecting element 13 which is secured about the ends 20, 21.

The connection between the ends 20 and 21 of the proximal and distalcore sections 11 and 12, respectively, may be made by positioning thedistal end 20 of the proximal core section 11 and the proximal end 21 ofthe distal core section 12 in close proximity to each other within theinterior of a mold which preferably has a cylindrical interior moldingsurface of the desired dimensions of the exterior surface 22 of theconnecting member 13. Polymerizable or otherwise hardenablenon-conductive material is introduced into the interior of the mold andpolymerized or otherwise hardened into a polymeric or other non-metallicmass about the ends 20 and 21 so as to fix the ends within theconnecting element 13. The hardenable non-conductive material formingthe connection between the proximal and distal core sections 11 and 12is sufficiently strong to facilitate torque transmission between thesecore sections.

Suitable non-magnetic, and preferably polymeric materials for theconnecting element 13 include one or more thermoplastic polymericmaterials such as a polyester, polyetheretherketone, ABS, and epoxymaterials or co-polymers or blends thereof. The polymeric materials maybe blends of a variety of polymeric materials. The polymeric material ispreferably selected so that the connecting element 13 holds the two coresections together to effect torque transmission and to provide a smoothtransition between the proximal and distal core sections 11 and 12,respectively.

The proximal section 11 of one embodiment of the guide wire 10 isfabricated from metals such as work hardened 304V stainless steel. Inorder to have similar tracking, torque, and push properties, proximalsections of polymeric and composite materials would ideally have similarproperties. One important property to match is stiffness both laterallyand axially while hardness is of lesser importance. To achieve thepreferred properties of a guide wire, any proximal shaft of a polymericmaterial would be a composite. Further, the polymer component may be athermoset or a thermoplastic. Exemplary of common thermosets includeepoxy, polyester, vinylester, cyanate ester, phenolic, polyurethane, andpolyimide. Suitable fiber reinforcement materials include fiberglass,s-glass, e-glass, graphite, Kevlar®, Twaron®, Nomex®, Spectra®,polyaramid, carbon, boron, and boron nitride.

Fiberglass components may also be used in fabricating the guide wire,recognizing that fiberglass is typically a composite of a polyesterresin with a glass fiber reinforcement. Guide wires fabricated entirelyfrom fiberglass, however, do not have the functional advantages of adistal metallic section 12 and metallic tip coil 17.

Composite guide wire structures of fiber reinforced polymeric materialsmay be made by methods of extrusion, pultrusion, injection molding,transfer molding, flow encapsulation, fiber winding on a mandrel, or layup with vacuum bagging. Epoxy resins are available from a variety ofmanufacturers including Ciba Specialty Chemicals, Shell Chemical, DowChemical, and Gougeon Brothers, Inc. Sources of carbon fiber includeHexcel Corp., Amoco, Toho, Rayon, and Toray. Exemplary of non-compositematerials for the non-conductive proximal section 11 include glass fiberoptics (available from Corning Glass and Seiko Instruments, Inc.) andceramics.

The examples set forth in detail below illustrate the fabrication of acomposite proximal shaft of a guide wire in accordance with the presentinvention. In the first exemplary embodiment, a composite proximal shaftis fabricated with IM7 carbon fibers (available from Hexcel Corp.) andan Epon epoxy resin system (available from Shell Corp.). Usingpultrusion, a shaft of 67 volume percent carbon fiber is fabricated. A20 cm distal section of nitinol is affixed to the shaft using a sleevejoint. A tip coil of 90/10 tantalum/tungsten alloy is attached bysoldering to the distal end of the nitinol section.

In the second exemplary embodiment, a composite proximal shaft isfabricated of Victrex™ PEEK 450CA30 (30% carbon reinforced) byextrusion. Optional bands of palladium are attached to the shaft at 10cm intervals to function as passive paramagnetic susceptibility markers.The 20 cm distal metallic shaft is fabricated of CP (commercially pure)titanium (Wah Chang). A 90/10 platinum/iridium tip coil is attached viasoldering to the titanium section.

As seen in FIG. 1, one embodiment of a guide wire 10 having features ofthe present invention generally includes an elongated core member withan electrically non-conductive proximal core section 11, a metallicdistal core section 12 with low magnetic susceptibility, and a metallictip coil 27 extending from the distal end of the distal core section 12.

The non-electrically conductive proximal core section 11 is MRI safewith regard to both attractive forces and RF heating effects. Thisdistal core section 12 between the non-conductive proximal core section11 and the tip coil 27 is analogous to the distal nitinol section of aconventional guide wire. Its maximum safe length can be estimated fromthe magnetic field strength of the MRI scanner. At 1.5 T, antenna theorypredicts that a guide wire can behave as a dipole antenna beginning at alength of 23 inches (about 58 cm).

Preferably, the metallic tip coil 27 and the distal core section 12 (theconductive members) are connected with a non-conductive insulator sothat they do not act in concert as a single dipole antenna. If themetallic tip coil 27 and the distal core section 12 are separated by anon-conductive material 13, then the length of the distal core section12 can be up to 23 cm in a magnetic field of 1.5 T. Without theinsulator, the 23 cm length applies to the total length of the tip coil27 and the distal core section 12.

As the RF frequency utilized is linearly proportional to the MRI scannerfield strength, lower field strengths of 1.0 T and 0.5 T couple atconductor member lengths of 35 cm and 69 cm, respectively. So at a lowermagnetic field strength of 1.5 T, a preferred range for the length ofthe conductive member is less than 29 cm. A more preferred range of thelength of the conductive member is less than 23 cm. The minimumpractical length of the conductive section is determined by the lengthof a functional guide wire tip coil which is approximately 3 cm. Thesemaximum safe lengths are inversely proportional to the magnetic fieldstrength.

The highest field strength MRI scanners in routine clinical use at thepresent time operate at 3 T. At this strength, a preferred conductorlength is less than approximately 14.4 cm, and a more preferredconductor length is less than approximately 11.5 cm. Thus, as the MRIscanner field strength increases, the safe length of the conductivemembers decreases.

Accordingly, the conductive member in one embodiment has a length ofabout L<43.5/B₀, where “L” represents the electrically conductive lengthin centimeters, and “B₀” represents the scanner magnetic field in Tesla.In a more preferred embodiment, the conductive member has a length ofabout L<34.5/B₀. The experimental and theoretical foundation for thesevalues may be found in the work of Liu et al., Journal of MagneticResonance Imaging, Vol. 12, pp. 75-78 (2000), and Nitz et al., Journalof Magnetic Resonance Imaging, Vol. 13, pp. 105-114 (2001), the contentsof which are incorporated herein by reference.

FIG. 7 illustrates another embodiment in which the length of themetallic distal core section (conductive member) is limited. Inparticular, the distal core section 12 may be formed in multiplemetallic segments 31 and 32 separated by a non-conductive joint 33. Thisconstruction provides a longer metallic distal core section with each ofthe metallic segments being kept short enough so as to not be heatedwhen subjected to the magnetic fields generated by the MRI to providegreater length distal sections.

The electrical conductivity of the non-conductive proximal core section11 is electrical resistivity expressed in micro-ohm-cm. The higher thevalue for electrical resistivity, the more resistance for the materialof the proximal core section. Based on research using nitinol guidewires, for example, it has been found that at about 100 micro-ohm-cm, anitinol guide wire is conductive enough to heat in an MRI scanner.However, little research has been done examining how conductive a longwire can be in an MRI and still avoid heating. Models of this effecthave considered resistance of the wire to be negligible. The minimumresistivity for the non-conductive proximal core section is estimated tobe approximately 0.01 ohm-cm.

The coil 16 may also be formed by two separate coil segments: a distalcoil segment 27 which is formed of a non-magnetic material having therequisite magnetic susceptibility to provide MRI visibility, and aproximal coil segment 28 which may be made of another material havingother desirable properties such as radiopacity. Additionally, the distalcoil segment 27 of the coil 16 may be stretched about 10 to about 30% inlength as shown in FIG. 1 to provide increased flexibility.

The elongated proximal core section 11 may be an optical fiber whichshould be provided with a coating 30 of lubricous material such as afluoropolymer, polytetrafluoroethylene sold under the trademark Teflon®by Du Pont de Nemours & Co. Other suitable lubricous coatings includefluoropolymers, hydrophilic coatings and polysiloxane coatings.

The overall length of the guide wire 10 will vary depending upon theprocedure and the MRI compatibility parameters mentioned above, but forpercutaneous intravascular procedures the guide wire is generally about100 to about 200 cm in length. Most commercially available guide wiresfor adult coronary use come in lengths of 175 cm and 195 cm. The outerdiameter of the guide wire ranges from about 0.006 to 0.018 inch(0.15-0.45 mm) for coronary use. Larger diameter guide wires, e.g. up to0.035 inch (0.89 mm) or more may be employed in peripheral arteries andother body lumens. The length of the distal core section can range fromabout 1 to about 30 cm, depending upon the flexibility and otherproperties including MRI imaging characteristics desired in the finalproduct. The helical coil 16 may be about 3 to about 45 cm in length,preferably about 5 to about 30 cm and may have an outer diameter aboutthe same size as the outer diameter of the elongated proximal coresection 11. The helical coil 16 is preferably made from wire about 0.001to about 0.003 inch (0.025-0.08 mm) in diameter, typically about 0.002inch (0.05 mm). The shaping ribbon 21 and the flattened distal section29 of distal core section 12 can have generally rectangular shapedtransverse cross-sections which usually have dimensions of about 0.0005to about 0.006 inch (0.013-0.152 mm), and preferably about 0.001 by0.003 inch (0.025-0.076 mm).

In an embodiment of the present invention, the distal core section 12 ismade of a metal or alloy material which has a volumetric magneticsusceptibility of less than about 280×10⁻⁶ (SI), and preferably lessthan about 245×10⁻⁶ (SI). Metals that meet this criteria and theirrespective volumetric magnetic susceptibility are set forth in thefollowing table. While the distal core section 12 needs to beessentially non-magnetic, it does not necessarily require the volumetricmagnetic susceptibility set forth above which provides visibility underMRI. VOLUMETRIC MAGNETIC MATERIAL SUSCEPTIBILITY (×10⁻⁶ (SI)) Platinum279 Nitinol 245 Niobium 237 Titanium 182 Tantalum 178 Zirconium 109Iridium 37.5 Aluminum 20.7 Silver −24 Gold −34 Indium −51

Various polymeric connecting elements 13 embodying features of theinvention generally have outer diameters from about 0.006 inch to about0.02 inch (0.15-0.51 mm), and preferably about 0.10 to about 0.014 inch(2.5-0.356 mm) for coronary guide wires. The overall length of theconnecting element 13 may range from about 0.25 to about 3 cm, andtypically ranges about 0.75 to about 1.5 cm. Naturally, the connectingelements for guide wires for other medical applications and treatmentsites may have dimensions different than that described above.

The proximal core section 11 is formed of a non-conductive material suchas an optical fiber (e.g., a single fiber or a bundle of fibers), carbonfiber epoxy composites, composites of oriented polyethylene fiber (e.g.,Spectra®), composites of polyaramide fiber (e.g., Kelvar®), andcomposites of these materials with engineering resins such aspolyaryetherketone, polyphenylenesulfide, polyimide andpolyetheretherketone. Other suitable non-conductive materials may beused for the proximal core section.

The guide wire embodying features of the invention may be percutaneouslyintroduced into a patient's blood vessel, such as the femoral artery,and advanced within the patient's vasculature under MRI so as to be ableto observe the coil at the guide wire distal core section which acts asan MRI visible marker member to ensure that the guide wire or otherintracorporeal device is disposed at a desired location within thepatient's vasculature. Once the distal portion of the guide wire is inplace at the desired location, a therapeutic or diagnostic device may beadvanced over the in place guide wire until the operative portion of theintracorporeal device is positioned to perform a therapeutic ordiagnostic procedure in a conventional fashion.

While the description of embodiments having features of the inventionhas been directed primarily herein to guide wires suitable for guidingother devices within a patient's body, those skilled in the art willrecognize that these features may also be utilized in otherintracorporeal devices such as electrophysiology catheters, pacing leadsand the like. References to other modifications and improvements can bemade to the invention without departing from the scope of the appendedclaims.

To the extent not otherwise described herein, the materials and methodsof construction and the dimensions of conventional intracorporealdevices such as intravascular guide wires may be employed with a deviceembodying features of the present invention. Moreover, featuresdisclosed with one embodiment may be employed with other describedembodiments. Additionally, reference to the terms “members,” “elements,”“sections” and terms of similar import in the claims which follow shallnot be interpreted to invoke the provisions of 35 U.S.C. § 112(paragraph 6) unless reference is expressly made to the term “means”followed by an intended function.

1. A guide wire, comprising: a core having a proximal core section withproximal and distal ends and a distal core section with proximal anddistal ends; and a non-conductive joint securing the distal end of theproximal core section to the proximal end of the distal core section;wherein the non-conductive joint is not covered by a hypotube.
 2. Theguide wire of claim 1, wherein the non-conductive joint encases at leastone of the distal end of the proximal core section and the proximal endof the distal core section.
 3. The guide wire of claim 1, wherein atleast one of the distal end of the proximal core section and theproximal end of the distal core section includes a taper.
 4. The guidewire of claim 1, wherein at least one of the distal end of the proximalcore section and the proximal end of the distal core section has anundulated shape.
 5. The guide wire of claim 1, wherein thenon-conductive joint includes at least in part one or more thermoplasticpolymeric materials selected from the group consisting of polyester,polyetheretherketone, ABS, epoxy, copolymers, and blends thereof.
 6. Aprocess for joining two guide wire core materials without using ahypotube, comprising: providing a proximal core section having a distalend and a distal core section having a proximal end; grinding at leastone of the distal end of the proximal core section and the proximal endof the distal core section; shaping at least one of the distal end ofthe proximal core section and the proximal end of the distal coresection into a geometric pattern; and at least partially encasing atleast one of the distal end of the proximal core section and theproximal end of the distal core section with a non-conductive material.7. The process of claim 6, wherein the non-conductive material includesat least in part of one or more thermoplastic polymeric materialsselected from the group consisting of polyester, polyetheretherketone,ABS, epoxy, copolymers, and blends thereof.
 8. The process of claim 6,further comprising forming a taper on at least one of the distal end ofthe proximal core and the proximal end of the distal core.
 9. Theprocess of claim 6, wherein the geometric pattern is an undulated shape.10. A guide wire, comprising: a core having a proximal core section withproximal and distal ends and a distal core section with proximal anddistal ends; and a non-conductive means securing the distal end of theproximal core section to the proximal end of the distal core section;wherein the non-conductive means is not covered by a hypotube.
 11. Theguide wire of claim 10, wherein the non-conductive means includes anon-metallic material.
 12. The guide wire of claim 10, wherein theproximal core section includes stainless steel.
 13. The guide wire ofclaim 12, wherein the distal core section includes nitinol.
 14. Theguide wire of claim 10, wherein the non-conductive means includes atleast in part one or more thermoplastic polymeric materials selectedfrom the group consisting of polyester, polyetheretherketone, ABS,epoxy, co-polymers, and blends thereof.
 15. The guide wire of claim 10,wherein the non-conductive means includes at least one of apolymerizable material and a hardenable non-conductive material.
 16. Theguide wire of claim 10, wherein the proximal end of the distal coresection and the distal end of the proximal core section do not overlieeach other.
 17. The guide wire of claim 10, wherein the proximal end ofthe distal core section and the distal end of the proximal core sectionhave respective flat faces that nearly abut each other.
 18. The guidewire of claim 10, wherein the proximal end of the distal core sectionand the distal end of the proximal core section do not directly contacteach other.